/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.io.mongodb;



import com.google.auto.value.AutoValue;

import com.mongodb.client.MongoCollection;

import com.mongodb.client.MongoCursor;

import com.mongodb.lang.Nullable;

import com.bff.gaia.unified.sdk.annotations.Experimental;

import com.bff.gaia.unified.sdk.transforms.SerializableFunction;

import org.bson.BsonDocument;

import org.bson.Document;



import java.util.ArrayList;

import java.util.List;



/** Builds a MongoDB AggregateIterable object. */

@Experimental(Experimental.Kind.SOURCE_SINK)

@AutoValue

public abstract class AggregationQuery

    implements SerializableFunction<MongoCollection<Document>, MongoCursor<Document>> {



  abstract List<BsonDocument> mongoDbPipeline();



  @Nullable

  abstract BsonDocument bucket();



  private static Builder builder() {

    return new AutoValue_AggregationQuery.Builder().setMongoDbPipeline(new ArrayList<>());

  }



  abstract Builder toBuilder();



  public static AggregationQuery create() {

    return builder().build();

  }



  @AutoValue.Builder

  abstract static class Builder {

    abstract Builder setMongoDbPipeline(List<BsonDocument> mongoDbPipeline);



    abstract Builder setBucket(BsonDocument bucket);



    abstract AggregationQuery build();

  }



  public AggregationQuery withMongoDbPipeline(List<BsonDocument> mongoDbPipeline) {

    return toBuilder().setMongoDbPipeline(mongoDbPipeline).build();

  }



  @Override

  public MongoCursor<Document> apply(MongoCollection<Document> collection) {

    if (bucket() != null) {

      if (mongoDbPipeline().size() == 1) {

        mongoDbPipeline().add(bucket());

      } else {

        mongoDbPipeline().set(mongoDbPipeline().size() - 1, bucket());

      }

    }

    return collection.aggregate(mongoDbPipeline()).iterator();

  }

}